496 THE RABBIT CHAP. 



trigeminal leaves the skull. 1 Between the mastoid portion 

 of the periotic and the posterior border of the tympanic, at 

 the junction of the tubular and bulbous portions of the 

 latter bone, is a small aperture the stylomastoid foramen, 

 which transmits the seventh nerve : this and the eighth 

 (VII, VIII) enter the periotic just below the depression for 

 the flocculus of the cerebellum (fi). A space (IX, X, XI) 

 between the occipital condyle and tympanic bulla gives exit 

 to the ninth and tenth, as well as to the eleventh which is 

 not represented as a distinct nerve in the dogfish and frog ; 

 and the hypoglossal (p. 160), which in Mammals is counted 

 as the twelfth cerebral nerve, passes out through two small 

 apertures (XII) in the exoccipital, just anterior to the 

 condyle. Various other apertures will be noticed in the skull 

 and jaws : through some of these branches of certain of the 

 above-mentioned nerves pass, while others transmit blood- 

 vessels. 



The lower jaw or mandible (Fig. 132, A) consists of 

 two halves or rami, each corresponding essentially to 

 the dentary of the frog, which unite with one another 

 in front, at the symphysis, by a rough surface, while 

 behind they diverge like the limbs of the letter V. 

 Each ramus is a vertical plate of bone, broad behind and 

 tapering towards the front, where it bears the incisor 

 teeth : further back, on its upper margin, are the sockets 

 for the cheek-teeth, and behind them is an ascending 

 portion which bears the condyle (cond) for articulation 

 with the facet on the squamosal : in front of the condyle 

 is a curved coronoid process (cor] . The postero-inf erior 

 border, which is rounded and inflected, is known as the 

 angular process (ang. pro). 



The hyoid is a small bone situated at the root of the 

 tongue, anterior to the larynx (Fig. 135, hy). It consists 

 of a stout body or basi-hyal, a pair of small anterior 

 horns, representing the ventral ends of the hyoid arch 



1 In many Mammals (e.g., dog, cat) the maxillary division of 

 the trigeminal passes out through a separate foramen, behind the 

 sphenoidal fissure ; and the anterior part of the space referred to 

 above is separated off as a distinct foramen for the mandibular 

 division. 



